Types of Operating Systems

1. Types of Operating Systems Computer Engineering Department Computer Graphics Course Asst. Prof. Dr. AhmetSayar Kocaeli University - Fall 2012

2. Uniprocessor Operating Systems • An OS acts as a resource manager or an arbitrator • Manages CPU, I/O devices, memory • OS provides a virtual interface that is easier to use than hardware • Structure of uniprocessor operating systems • Monolithic (e.g., MS-DOS, early UNIX) • One large kernel that handles everything • Layered design • Functionality is decomposed into N layers • Each layer uses services of layer N-1 and implements new service(s) for layer N+1

3. Uniprocessor Operating Systems • Microkernel architecture • Small kernel • user-level servers implement additional functionality

4. Distributed Operating System-Multi-computer- • Manages resources in a distributed system • Seamlessly and transparently to the user • Looks to the user like a centralized OS • But operates on multiple independent CPUs • Provides transparency • Location, migration, concurrency, replication,… • Presents users with a virtual uniprocessor

5. Multi-computer Systems • How to run multiprocessor software on multicomputer systems ?

6. Multiprocessor Operating Systems • Multi-core • Like a uniprocessor operating system • Manages multiple CPUs transparently to the user • Shared main memory and controlled by a single OS instance • Each processor has its own hardware cache • Maintain consistency of cached data

7. Multiprocessor Operating - Contd SystemsHardware Concept

8. Multiprocessor Operating Systems -Contd • A bus-based multiprocessor • A representation of shared memory super computing

9. Distributed Operating Systems (1) • Example: MOSIX cluster - single system image

10. Distributed Operating Systems (2) • Gives illusion of single system • Users not aware of multiplicity of machines • Access to remote resources similar to access to local resources • Data Migration – transfer data by transferring entire file, or transferring only those portions of the file necessary for the immediate task • Computation Migration – transfer the computation, rather than the data, across the system

11. Network Operating System (1)

12. Network Operating System (2) • Users are aware of multiplicity of machines. Access to resources of various machines is done explicitly by: • Remote logging into the appropriate remote machine (telnet, ssh) • Remote Desktop (Microsoft Windows) • Transferring data from remote machines to local machines, via the File Transfer Protocol (FTP) mechanism

13. Middleware-based Systems

14. Types of Distributed OSs

15. Comparison between Systems

16. Pitfalls when Developing Distributed Systems • False assumptions made by first time developer: • The network is reliable. • The network is secure. • The network is homogeneous. • Latency is zero. • Bandwidth is infinite. • Transport cost is zero. • There is one administrator.

17. Summary • Distributed Systems … autonomous computers • working together to give the appearance of a single, coherent system. • They are transparent, scalable and open. • Unfortunately, they also tend to be complex

18. Overview challenges • Concurrency • Shared access to resources must be possible • Openness • Interfaces should be publicly available to ease adding new components • Security • The system should only be used in the way intended